In the construction of residential and commercial buildings it is common to have back-to-back bathrooms wherein the hot and cold water supply pipes service shower and tub units on opposite sides of the wall. Prior art shower control valves often have the cold water inlet on one side and the hot water inlet on the other side. As the two supply pipes in the wall are normally side-by-side, it is necessary to provide an awkward cross-over arrangement for one of the shower units. Later inventions provided shower control valve assemblies that utilise a casing having two inlets and a replaceable cartridge unit which can be adjusted in a relatively simple manner at the time of installation so that it is entirely optional as to which of the inlets is connected to the hot water supply pipe and which is connected to the cold water pipe. Commonly assigned Canadian Patent No. 1,050,853 of Mar. 20, 1979 discloses just such an arrangement. The valve assembly of that patent is pressure balanced, with a single handle to control the temperature and the pressure of the water issuing from the shower. The casing of the patented valve assembly included a single outlet leading to the shower, water for the tub flowing through a separate spout having a diverter valve associated therewith.
The trend in pressure balanced valve assemblies has been towards single handle control valves which are also adapted to control the flow of water to a tub as well as to a shower. U.S. Pat. Nos. 4,681,140; 4,901,750; and 4,905,732 all teach single handle pressure, temperature and/or volume balanced mixing valves.
One of the problems associated with any water flow arrangement is that of water hammer, generated noise which is frequently experienced in pressure sensing mixing valves when they are installed in line with quick closing faucets or diverter valves. Other problems involve cross flow between the hot and cold water supply lines, back flow in either or both of the supply lines, and wear of the rubber seal that contacts the mixing disc of the valve.
Commonly assigned Canadian Patent Application No. 2,076,924 filed Aug. 26, 1992 teaches a single handle pressure and temperature balancing mixing valve assembly that includes, among other features, a check valve at each of the hot and cold water inlets to prevent cross flow between the hot and cold water supply lines, to prevent back flow to either supply line, and to eliminate the effects of water hammer. Additionally, or optionally, the valve casing may include separate outlets for the tub and for the shower, with there being a built-in bypass or diverter channel to divert water from one outlet to the other and the entire valve cartridge may be rotated through 180.degree. to reverse the hot and cold inlets.
Commonly assigned Canadian Patent Application No. 2,109,034 filed Oct. 21, 1993 provides an improvement to the aforementioned application by having the mixing disc in constant contact with a pair of axially movable seat members and by having each seat member contact a fixed O-ring seal in the closed position of the valve disc. The O-ring is free from contact with any of the moving components of the valve per se. Sealing contact of the O-ring is made only at the valve closing position, thus reducing torque and eliminating wear. Each axially movable seat member is made of a plastics material having a low friction property. The seat members are held in contact with the mixing disc by water pressure only. A circular wave spring place under a snap seal that holds the O-ring exerts enough force to seal the water at low supply pressures. The wave spring also takes up any slack due to the natural wear between the axially movable seat member and a cam surface on the mixing disc.
Another area requiring improvement with such pressure balanced valves is the diverter valve that is used to divert water from the tub faucet to the shower nozzle. The most common type of diverter involves a valve actuator positioned in the faucet itself, such that raising the actuator while water is flowing through the faucet will close the diverter valve and cause the water to be forced to the shower nozzle. If the user of the shower is already in the tub enclosure he or she will have to bend over to actuate the diverter, an inconvenience at the least. Also, such diverter valves are strictly of the "on/off" variety; they do not have the capability of any volume, pressure or temperature adjustment. If there is any failure of the diverter valve it is necessary to dismantle the faucet and the attendant valve structure to effect repair, a time consuming and possibly expensive proposition. There is therefore a need for a more-convenient, adjustable, and easily repaired diverter valve structure for pressure balanced valve installations.